Stock prices hovered in a narrow range today in a sluggish summer session. The Dow Jones average of 30 industrials, down about 8 points in early trading, was up .89 at 2,132.11 by 2 p.m. on Wall Street. Gainers and losers ran about even in the overall tally of New York Stock Exchange-listed issues, with 692 up, 688 down and 485 unchanged. Volume on the Big Board came to 153.59 million shares with two hours to go. Nearly half of that activity was concentrated in a single issue _ American Electric Power, unchanged at 28}. Analysts said the heavy trading in the stock stemmed from trading strategies focused on the company's impending dividend. Otherwise, analysts said the market was still beset by concerns that strong economic growth would prompt further moves by the Federal Reserve to restrain inflation. The Labor Department's monthly report Friday on the employment situation for July is expected to show continuing robust gains in payroll employment In the credit markets today, prices of long-term government bonds, which move in the opposite direction from interest rates, declined slightly. Insilco jumped 6\ to 27{ on word that the company's management is considering a buyout proposal. Texaco, trading ex-dividend, rose } to 47|, and Texaco Canada added [ to 30~ on the American Stock Exchange. On Tuesday Texaco said its 78 percent stake in Texaco Canada was for sale. The NYSE's composite index of all its listed common stocks gained .25 to 153.79. At the Amex, the market value index was down .34 at 306.16.